mathnet-numerics/src/UnitTests/IntegralTransformsTests/HartleyTest.cs

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using System;
using MathNet.Numerics.Distributions;
using MathNet.Numerics.IntegralTransforms;
using MathNet.Numerics.IntegralTransforms.Algorithms;
using MathNet.Numerics.Signals;
using NUnit.Framework;

namespace MathNet.Numerics.UnitTests.IntegralTransformsTests
{
    using Random = System.Random;

#if NOSYSNUMERICS
    using Complex = Numerics.Complex;
#else
    using Complex = System.Numerics.Complex;
#endif

    /// <summary>
    /// Hartley tests.
    /// </summary>
    [TestFixture]
    public class HartleyTest
    {
        /// <summary>
        /// Continuous uniform distribution.
        /// </summary>
        IContinuousDistribution GetUniform(int seed)
        {
            return new ContinuousUniform(-1, 1, new Random(seed));
        }

        /// <summary>
        /// Verify if matches DFT.
        /// </summary>
        static void VerifyMatchesDft(
            double[] samples,
            int maximumErrorDecimalPlaces,
            bool inverse,
            Action<Complex[]> dft,
            Func<double[], double[]> hartley)
        {
            var hartleyReal = hartley(samples);

            var fourierComplex = ArrayHelpers.ConvertAll(samples, s => new Complex(s, inverse ? -s : s));
            dft(fourierComplex);
            var fourierReal = ArrayHelpers.ConvertAll(fourierComplex, s => s.Real);

            AssertHelpers.ListAlmostEqual(fourierReal, hartleyReal, maximumErrorDecimalPlaces);
        }

        /// <summary>
        /// Native matches DFT.
        /// </summary>
        /// <param name="hartleyOptions">Hartley transformation options.</param>
        /// <param name="fourierOptions">Fourier transformation options.</param>
        [TestCase(HartleyOptions.Default, FourierOptions.Default)]
        [TestCase(HartleyOptions.AsymmetricScaling, FourierOptions.AsymmetricScaling)]
        [TestCase(HartleyOptions.NoScaling, FourierOptions.NoScaling)]
        public void NaiveMatchesDft(HartleyOptions hartleyOptions, FourierOptions fourierOptions)
        {
            var dht = new DiscreteHartleyTransform();
            var samples = SignalGenerator.Random(x => x, GetUniform(1), 0x80);

            VerifyMatchesDft(
                samples,
                5,
                false,
                s => Transform.FourierForward(s, fourierOptions),
                s => dht.NaiveForward(s, hartleyOptions));
            VerifyMatchesDft(
                samples,
                5,
                true,
                s => Transform.FourierInverse(s, fourierOptions),
                s => dht.NaiveInverse(s, hartleyOptions));
        }
    }
}